Tenant wants to break lease

[Cali Skier]

Hi,

We have tenants that are 7 months into the lease and bought a house.  Now they want to break the lease, we told the the terms and give them an alternative the give them their deposits back, but they have stopped communicating and will not tell us when they plan to leave and have not provide a forwarding address.  I am assuming that come March I am not going to get a rent payment and I am going to find the house empty.  

My agreement allows for them to break the lease with penalty and rent must be paid until it gets re rented, i can't list it because they have not formally stated they wish to break the lease, its all verbal.

What is my next step to force them to pay rent?